The present invention relates to a method for preparing error entries of the users of a data bus in a motor vehicle.
Typical users of a data bus, in particular control units in a motor vehicle, have the capability of detecting errors of their own operation and/or errors of the output behavior, e.g., the transmission behavior, of other users of the data bus. Such errors may be of various types, for example, temporary or permanent, safety-critical or not safety-critical, service-relevant or not service-relevant. In this context, service-relevant errors are those whose occurrence typically causes a service action such as the replacement or the repair of a unit in a service station in case of correct detection.
Modern motor vehicles typically contain several dozen control units. When an error is detected at one user of a data bus, the user detecting the error typically instigates an error entry in an error memory independently of the type of error. This error entry may be entered by the detecting user itself in a local error memory or the detecting user may instigate another user to perform a corresponding error entry.
A very large quantity of error entries may accumulate in one or more error memories of a motor vehicle by instigating an error entry for each detected error independently of the type of error. These error entries are typically read out via a diagnostic system, for example, in a service station, during an error search, and a large number of error entries makes the targeted error search difficult. The large number of errors which are not service-relevant prevents the quick and simple discovery of service-relevant errors.
In addition, the hardware of an error memory is unnecessarily strained by the high number of write cycles due to an unnecessarily high occurrence of error entries. This may result in exceeding the number of write cycles provided in the specification of the hardware of the error memory and/or breakdown or malfunctions of the hardware of the error memory.
Modern diagnostic systems have the option of masking error entries as a function of specific criteria, such as their safety relevance, in order to identify safety-critical errors quickly and easily. However, depending on how the criteria are established specific errors can be incorrectly masked. For example, the service relevance of an error frequently may not be derived solely from the type of error. Instead, determining the service relevance frequently requires additional information, such as information on specific vehicle states at the time of the occurrence of the error or in the time following the occurrence of the error. Accordingly, masking depending on criteria of the type of error may result in error entries of service-relevant errors being overlooked.
German Patent Document No. DE 10107367 A1 discloses a method for diagnosing using error pattern detection with assignment of one or more error symptoms to a physical error. The error systems are situated in an error pattern, the error pattern is logically linked to one more matrices, and the matrices contain information about the error patterns of known physical errors. The method offers the possibility of avoiding repeated entries in an error memory as a result of repeatedly occurring errors by detecting the associated error pattern. However, this method requires a very high storage and computing outlay. In addition, errors of an error pattern not yet stored in the error memory, which are not service-relevant in certain circumstances, are entered in the error memory at least once.
Exemplary embodiments of present invention provide a simple method for preparing error entries of the users of a data bus in a motor vehicle, in which unnecessary error entries are avoided.
Exemplary embodiments of the present invention provide a method in which upon detecting a possibly service-relevant error, the detecting user is put in an error state and outputs an error message to a second user, upon which a request to prepare an error entry is output to the detecting user by the second user as a function of at least one predefined condition, preferably establishing a state in which the detected error is function-impairing, or the transition of the motor vehicle into such a state, and an error entry is instigated by the detecting user in case of receiving such a request.
By interposing the at least one condition checked by the second user, unnecessary error entries may be avoided.
According to an exemplary embodiment of the present invention, errors which are detected by one of the users are first assigned to at least one of two classes as a function of their error type. Depending on the error type and/or class, an error entry is then immediately instigated or a method as described above is used. Upon detection of an error of at least one first class, such as the class of safety-relevant and/or in any case service-relevant errors, an error entry is immediately instigated by the detecting user. Upon detection of an error of at least one second class, such as the class of errors which are not safety-relevant and only service-relevant under certain circumstances, the detecting user is put into an error state and an error message is output to a second user, upon which a request to prepare an error entry is output to the detecting user by the second user as a function of at least one condition and an error entry is instigated by the detecting user in case of receiving such a request.
By assigning the error to at least two classes, the possibility exists of storing errors of at least one specific class in any case, while errors of at least one other class may be checked more closely for the necessity and/or advisability of an error entry.
An error entry to be performed may be entered by the detecting user itself in a local error memory or the detecting user may instigate another user to perform a corresponding error entry. For example, instigating an error entry in a central error memory or instigating an error entry in the error memory of a user which is closer to the error source in a hierarchical structure than the detecting user is conceivable for this purpose.
Both the error detection and also performing error entries may be cascaded. For example, a user A, which has detected an error, may put itself in an error state and output an error message to a user B, the user B has thus also detected the error, puts itself in an error state and outputs an error message to a user C, the user C then outputs a request to prepare an error entry to the user B after receiving the error message as a function of at least one predefined condition, the user B outputs a request to prepare an error entry to the user A as a function of a predefined condition, namely receiving the request of the user C, upon which the user A performs the error entry.
A method according to the present invention is particularly suitable for use in a hierarchical structure of users. If a method according to the present invention is used in a function-related hierarchical structure, for example, a higher-order user typically decides whether a lower-order user is to perform or instigate an error entry.
A user which detects an error, transmits an error message, and has put itself in an error state typically initially remains in this error state. This error state may be connected to restrictions of the function of the user and is not to be maintained for an unnecessarily long time. An efficient procedure to cancel the error state as soon as possible, but not too early, is to cancel the error state after the expiration of a predefined time constant, during which the detecting user is in the error state, but has not received a request for error storage. It may also be expedient to cancel the error state after the occurrence of at least one predefined event. In particular, such an event may comprise the cessation of the error which has resulted in the transition into the error state, the detection of such a cessation, or a request not to enter the error being received. According to an advantageous embodiment of the present invention, an error state of a detecting user is thus canceled after the expiration of a predefined time constant without receiving a request to instigate an error entry and/or after the occurrence of at least one predefined event, in particular the cessation of the error.
To avoid synchronization problems when a cancellation of the error state triggered by an event, the error state can be canceled at the earliest after the expiration of a predefined time constant which is to be measured from the cessation, its establishment, and/or another event.
A further advantage of a method according to the present invention is that the efficient control of the storage of error entries may also be used for efficiently controlling warning notifications to the driver of the motor vehicle. It is also true for warning notifications to the driver, as for the storage of error entries, that as much as possible only safety-relevant and service-relevant errors are to be displayed. Correspondingly, according to a refinement of the present invention, a warning notification is immediately instigated upon occurrence of an error of a specific class, e.g., a safety-relevant error. In contrast, upon occurrence of an error of another class, e.g., an error which is not safety-relevant and only possibly service-relevant, a warning notification is only, and at earliest, output when one of the users outputs a request or an instigation for an error entry.
According to an exemplary embodiment of the present invention, such a warning notification is instigated by the user who outputs the request to prepare an error entry quasi-simultaneously with the output of the request.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.